Synthesis of novel ptm radical derivatives and surface functionalization
- Autores: Malena Oliveros Collantes
- Directores de la Tesis: Jaume Veciana i Miró (dir. tes.), Veronica Mugnaini (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2011
- Idioma: español
- Tribunal Calificador de la Tesis: Gian Piero Spada (presid.), Marta Mas Torrent (secret.), Roser Pleixats i Rovira (voc.)
- Materias:
- Texto completo no disponible (Saber más ...)
- Resumen
Nowadays, the development of new molecular materials is focused on the prepa- ration of systems with specific properties that are related mainly to the presence of a particular molecular building block.
PTM radical derivatives are versatile and suitable molecular building blocks for functional materials thanks to their unique properties: electroactivity, lumines- cence and paramagnetism associated to their open-shell electronic configuration.
In this Thesis such unique properties have been used and widely studied to prepare new functional materials.
In the first part of this Thesis work we assayed different synthetic routes to prepare novel PTM radical derivatives substituted in the para position(s) with one (three) phosphonate group(s). The introduction of the phosphonate groups to form the phosphonate radical derivatives 4A, 5A and 6A was successful only through the formation of a lithiated intermediate formed from derivative 13 by reaction with diethylchlorophosphonate (ClP(O)(OEt)2).
In addition, a new synthetic route through the formation of a lithiated inter- mediate for the preparation of radical 1 was carried out. The reaction has a small number of steps and a higher global yield than the previous reported synthesis.
In the second part of this Thesis we were able to organize radical 2 for the first time on a Au(111) surface by UHV deposition. Even though in the literature are reported several examples of the organization of planar molecules onto differ- ent surfaces, this is one of the few example of deposition of a no planar molecule and of the STM imaging of its lateral hydrogen bonded assembly. The successful sublimation in UHV of an open-shell molecule, the radical 2 without signs of de- composition, was demonstrated by XPS, RAIRS, HREELS and EPR techniques. We were able to image the radical surface 2/Au(111) system by STM and to study the 2D hydrogen bonded assemblies of such non planar derivative. Two types of assemblies were seen at room temperature, thus suggesting a different kinetic stability of two domains. In both cases we observed the supramolecular organizations hydrogen bonded driven by the presence of the carboxylic moieties of the radical 2. The supramolecular organization resulted different from the one formed in bulk crystals and followed the main surface directions of Au(111). A modelling study confirmed that the observed ordering, dominated by intermolecular H-bonding, is explained on the basis of the role exerted by the surface and related to the absence of a multilayer. One type of assembly was imaged at low temperatures. Unexpectedly by lowering the imaging temperature the higher resolution achieved allowed to observe chiral helicity at the molecular level.
The experiments reported in the third part of the Thesis have demonstrated that the radical derivatives 1Na and 2Na3 can be successfully infiltrated into porous SiO2 and TiO2 thin films prepared by the GLAD technique onto a quartz substrates. Two methodologies have been used to favour this type of electrostatic interactions: 1) direct electrostatic binding of carboxylate PTM derivative 2Na3 to the positively charged oxide surface and; 2) binding of derivatives 1Na or 2Na3, mediated by a positively charged aminosilane anchoring layer. In both cases the resulting hybrid composites are paramagnetic and fluorescent.
In addition, by depositing the TiO2 host thin film on an ITO conductive and transparent film, it was possible to fabricate switchable hybrid organic-inorganic thin films where the optical (absorption and fluorescence) and magnetic properties can be reversibly switched on and off by applying external cyclic voltages. The switching behaviour, the easy handling as well as the robustness of these novel PTM radical-oxide composite thin films are essential conditions for the future development of robust electro-photonic/magnetic devices.
The synthesis of the radical derivative 2Na3 with high purity level has en- abled the use of it as promising and novel polarizing agent in DNP experiments.
The work described in this Thesis has contribuited to explore new method- ologies to obtain multifunctional hybrid materials using PTM radical derivatives as building blocks for applications in different fields of materials and surface science.
